1. Field of the Invention
The present invention relates to a developing apparatus which makes a toner adhere to a photoconductor and according to more detailed description, the present invention relates to a developing apparatus which makes conductive toner charged and makes the charged toner adhere to the photoconductor and also relates to an image forming apparatus provided with the developing apparatus and a toner replenishing method.
2. Description of the Related Art
According to outline of a process of forming an image of an image forming apparatus such as a printer or a copying machine or the like, toner charged in an apparatus housing the toner in advance is made adhere to an electrostatic latent image formed on a surface of a photoconductor roller by using a developing roller located close to the photoconductor roller and thereby developing is performed and a toner image which becomes an apparent image is transferred to a printing sheet and is fixed and thereby printing is performed on a recording sheet.
Therefore, it is required that toner should be in advance charged on the occasion of printing on the recording sheet. Consequently, when insulating toner is used, for instance, charge control material is mixed with the toner in the apparatus housing toner by using a stirring blade or the like and friction is applied to the toner and the charge control material and the toner is charged.
However, when friction is applied to the toner and the charge control material by stirring them, there are problems that the toner and the charge control material are segregated and separated from each other without being sufficiently mixed with each other and the toner deteriorates by friction stress.
Consequently, technique for using the conductive toner instead of the insulating toner is proposed.
When the conductive toner is used, the surface of the photoconductor roller and the surface of the developing roller are located without touch with each other so that a predetermined distance can be given between these surfaces. And when voltage is applied to a position between the surface of the photoconductor roller and the surface of the developing roller, the conductive toner on the developing roller is charged and is moved to the photoconductor roller and adheres to the electrostatic latent image.
The following description is given about a developing apparatus in Japanese Unexamined Patent Publication JP-A 2-199484 (1990) as a prior art for performing developing.
As shown in FIG. 10, this image forming apparatus 100 is provided with a toner transporting body (developing roller) 102 supplying toner to a latent image carrier (photoconductor roller) 101, a sleeve (replenishing roller) 103 and a blade 104 regulating a thickness of a layer of the toner supplied to the toner transporting body. The toner transporting body is configured with an insulating layer coated on a surface of the roller shape conductive support.
Voltage is respectively applied to a position between the conductive support of the toner transporting body and the sleeve 103 and to a position between the sleeve 103 and the blade 104 of the toner transporting body from voltage applying means 105. In addition, voltage is applied to a position between the conductive support of the toner transporting body and the latent image carrier by developing bias applying means 106.
Conductive toner is successively supplied from the sleeve to the toner transporting body and from the toner transporting body to the latent image carrier by using the above mentioned configuration.
A sensor located in the developing apparatus detects temperature and humidity or the like and an amount of toner which will be developed is kept constant by changing electric field between the conductive support and the blade according to a result of detecting the temperature and the humidity or the like.
In addition, the following description is given about an image forming apparatus in Japanese Unexamined Patent Publication JP-A 2001-277594 (2001) as another prior art with use of conductive toner.
This image forming apparatus forms an image by exposing a photoconductor filled with charged optical conductive toner from a back surface of the photoconductor and inverting polarity of the toner and making the toner fly on a side of an optical recording medium.
Using the optical conductive toner prevents diffusion of electric charge in an orthogonal direction to a flying direction equal to a plane direction of the photoconductor for the toner before flying at the time of exposing the toner to restrain deterioration of resolution.
In a developing apparatus in Japanese Unexamined Patent Publication JP-A 2-199484 (1990), supplying toner from the toner transporting body to the latent image carrier is performed without being in contact with each other, but supplying the toner from the sleeve to the toner transporting body is performed with being in contact with each other and therefore there is occurrence of mechanical stress for toner sandwiched between the sleeve and the toner transporting body and the toner deteriorates. In addition, driving torque given between the sleeve and the toner transporting body becomes greater and an amount of consumption of driving power increases.
In an image forming apparatus in Japanese Unexamined Patent Publication JP-A 2001-277594, when toner having electric charge is made fly, electrostatic repulsion is caused by each toner and when toner reaches the recording medium, the toner is diffused in a direction of the surface of the photoconductor and resolution deteriorates. In addition, this image forming apparatus uses exposure on a back of a belt, but in this case, since an exposing apparatus is located in a photoconductor roller, there is occurrence of problems that the image forming apparatus becomes large and complicated. Furthermore, there is also a problem that optical conductive toner has restriction in composition component in comparison with conductive toner and thereby handling the optical conductive toner is bothersome and the image forming apparatus requires cost.